Add missing init hook

http://python-notes.curiousefficiency.org/en/latest/python_concepts/import_traps.html#the-init-py-trap

tests/check_missing_inits_test.py

@@ -0,0 +1,62 @@
+import os
+
+import pytest
+
+from pre_commit_hooks.check_missing_inits import main
+
+
+@pytest.fixture
+def filepaths(tmpdir):
+    dirs = ['a', 'b']
+    files = ['a.py', 'b.py', '__init__.py']
+    paths = []
+    for d in dirs:
+        directory = tmpdir / d
+        os.mkdir(str(directory))
+        for f in files:
+            path = (directory / f)
+            paths.append(str(path))
+        # Nested directory
+        if d == 'b':
+            directory = directory / 'c'
+            os.mkdir(str(directory))
+            for f in files:
+                path = (directory / f)
+                paths.append(str(path))
+    return paths
+
+
+def test_has_inits(filepaths):
+    for f in filepaths:
+        with open(f, 'w'):
+            pass
+
+    assert main(argv=filepaths) == 0
+
+
+def test_missing_inits(filepaths):
+    remove = ''
+    for f in filepaths:
+        # Remove the init py file from the b directory
+        if os.path.join('b', '__init__.py') in f:
+            remove = str(f)
+            continue
+        with open(f, 'w'):
+            pass
+    filepaths.remove(remove)
+
+    assert main(argv=filepaths) == 1
+
+
+def test_nested_dirs_missing_inits(filepaths):
+    remove = ''
+    for f in filepaths:
+        # Remove the init py file from a nested directory
+        if os.path.join('b', 'c', '__init__.py') in f:
+            remove = str(f)
+            continue
+        with open(f, 'w'):
+            pass
+    filepaths.remove(remove)
+
+    assert main(argv=filepaths) == 1